Motorcycle tire for running on rough terrain

Abstract

A motorcycle tire for running on rough terrain comprises a tread portion having a unidirectional tread pattern and provided with T-sided blocks having a top surface, a heel-side sidewall surface extending from a heel-side edge of the top surface, and a toe-side sidewall surface extending from a toe-side edge of the top surface. The heel-side sidewall surface has an inclination angle α of from 0 to 15 degrees. The toe-side sidewall surface has a radially outer region having a height of from 20 to 55% of the block height and inclined at an angle β of from 20 to 45 degrees. A radially inner region of the toe-side sidewall surface has: a central part inclined at the same angle β as the radially outer region; a pair of lateral parts located one on each side of the central part and having an inclination angle γ of from 0 to 15 degrees; and a pair of stepped parts extending between the lateral parts and the central part in a direction crosswise to the toe-side edge.

The invention claimed is: 
     
       1. A motorcycle tire for running on rough terrain comprising
 a tread portion provided with a plurality of blocks defining a unidirectional tread pattern for which a tire rotational direction is specified, 
 the blocks including a T-sided block, 
 the T-sided block having a top surface, a heel-side sidewall surface extending radially inwardly from a heel-side edge of the top surface, and a toe-side sidewall surface extending radially inwardly from a toe-side edge of the top surface, wherein 
 in a cross section perpendicular to the top surface and parallel to the tire circumferential direction, the angle α of inclination of the heel-side sidewall surface towards the heel-side is, at the heel-side edge, in a range of from 0 to 15 degrees with respect to the normal direction to the top surface, 
 the toe-side sidewall surface comprises 
 
       a radially outer region extending radially inwardly from the toe-side edge so as to have a height of from 20 to 55% of the height of the T-sided block, and 
       a radially inner region extending radially inwardly from the radially outer region,
 said radially outer region is inclined toward the toe-side at an angle β of from 20 to 45 degrees with respect to the normal direction to the top surface at the toe-side edge, 
 the radially inner region has 
 a central part extending at the same angle β as the radially outer region, 
 a pair of lateral parts located one on each side of the central part and having at an inclination angle γ toward the toe-side in a range of from 0 to 15 degrees with respect to the normal direction, and 
 a pair of stepped parts extending between the lateral parts and the central part in a direction crosswise to the toe-side edge. 
 
     
     
       2. The motorcycle tire according to  claim 1 , wherein
 the total length of the paired lateral parts at their radially outer edge measured in the direction along the toe-side edge is in a range of from 12 to 60% of the length of the toe-side edge. 
 
     
     
       3. The motorcycle tire according to  claim 1  or  2 , wherein
 the blocks include crown blocks the centroids of the ground contacting top surfaces of which are disposed in a tread crown region defined as having a developed width of 40% of the tread developed width, and 
 at least one of the crown blocks is said T-sided block. 
 
     
     
       4. The motorcycle tire according to  claim 1  or  2 , wherein
 the blocks include crown blocks the centroids of the ground contacting top surfaces of which are disposed in a tread crown region defined as having a developed width of 40% of the tread developed width, and 
 the crown blocks are the T-sided blocks and non-T-sided blocks alternately disposed in the tire circumferential direction. 
 
     
     
       5. The motorcycle tire according to  claim 3 , wherein
 the blocks include middle blocks the centroids of the ground contacting top surfaces of which are disposed in a pair of tread middle regions defined as extending axially outwardly from the axial edges of the crown region and each having a developed width of 20% of the tread developed width, and 
 at least one of the middle blocks is said T-sided block. 
 
     
     
       6. The motorcycle tire according to  claim 5 , wherein
 the middle blocks are at least partially overlap the crown blocks in the tire axial direction. 
 
     
     
       7. The motorcycle tire according to  claim 4 , wherein
 the blocks include middle blocks the centroids of the ground contacting top surfaces of which are disposed in a pair of tread middle regions defined as extending axially outwardly from the axial edges of the crown region and each having a developed width of 20% of the tread developed width, and 
 at least one of the middle blocks is said T-sided block. 
 
     
     
       8. The motorcycle tire according to  claim 7 , wherein
 the middle blocks at least partially overlap the crown blocks in the tire axial direction.